Intraocular pressure changes in eyes with small incision lenticules and laser in situ keratomileusis

Measuring intraocular pressure after refractive surgery is a challenge in the diagnosis, evaluation, and treatment of glaucoma. Intraocular pressure characteristics after laser in situ keratomileusis (LASIK) are well known. However, intraocular pressure measurement and characteristics after small incision lenticule extraction (SMILE) are still unknown, providing an interesting point of comparison in terms of biomechanical differences from LASIK.

An intraocular pressure analytical model utilising fluid dynamics (simulating air puff) was developed using OpenFoam and Scilab. In addition, solid mechanics (simulating the deformation of the corneal structure) and a ray-tracing technique (simulating applanation detection) simulated by a previously established air-puff Tonovue tonometer were used to simulate post-SMILE and post-LASIK intraocular pressure.

Based on the proposed model, while at a myopic correction of zero dioptres the difference in intraocular pressure before and after SMILE was 0 mmHg, whereas the difference before and after LASIK was -2.2 mmHg. This trend was observed with a myopic correction up to 12 dioptres.

In a numerical simulation, differences in intraocular pressure in LASIK and SMILE largely resulted from the completeness of the Bowman's membrane resulting from cap or flap creation.